When being transported or stored, water for household use may be polluted by inorganic substances or organic substances during transportation or in the storage environment, a great amount of substances harmful to a human body can thus be found in water for household use, such as bacteria, viruses, or other microorganisms which can cause water deterioration. Accordingly, in order to enable water for household use to reach standard of general use, chemicals (germicides or detergents) are added most of the time in water for household use, for example, sodium chlorate may be added, or gaseous chlorine may be introduced to water. Moreover, with the oxidation reaction in water body through adding sodium chlorate or introducing gaseous chlorine, free available residual chlorine (HOCl+OCl−) or other oxidation substances may exist in water, so as to ensure that no bacteria are breeding or other harmful substances exist in water before use.
Nevertheless, in the process of deodorization and sterilization through adding chlorine, organic substances in water may react with free available residual chlorine, and trihalomethanes are thus formed. Trihalomethanes are volatile organic compounds with a boiling point of approximately 40° C. As such, when water containing trihalomethanes reaches a temperature higher than the boiling point of trihalomethanes, trihalomethanes vaporize and are likely to enter human body via respiration or dermal absorption; as a result, the central nervous system of the human body declines in function, leading to symptoms such as dizziness, fatigue, headache, liver toxicity, and renal toxicity. Besides, uptake of excessive level of trihalomethanes may even cause cancer in humans.
Accordingly, after chlorine is added to water for sterilization, free available residual chlorine in water needs to be removed through a dechlorination device. Nevertheless, a conventional dechlorination device has a complex structure and a considerable large size, and thus, the conventional dechlorination device is suitable to be installed in specific places in order to be used. For instance, in a general household, the conventional dechlorination device is suitable to be installed in the accommodation space under the sink for water to be dechlorinated. Furthermore, the conventional dechlorination device is filled with calcium sulfite or zinc-copper alloy as an adsorbent to adsorb free available residual chlorine in water. Nevertheless, the filled absorbent may contaminate water after the water is in contact with the absorbent for a long period of time, and thus, the absorbent in the dechlorination device has to be replaced periodically. Moreover, significant amount of operational power is needed to ensure smooth running of the conventional dechlorination device, and thus, costs of the conventional dechlorination device considerably increase accordingly. As such, the conventional dechlorination device is not widely applicable to other types of water supply equipment as limited by its large size and excessive energy consumption.
To sum up, a device with high efficiency and a simple structure to remove free available residual chlorine in water is needed urgently nowadays. Such device is to be widely applied to facilities for household use, so as to prevent free available residual chlorine in water from bring harm to the human body.